Slub yarn and method of forming a slub yarn

ABSTRACT

A fibrous sheet of 85-98 percent by weight synthetic fiber staple blended with 2-15 percent by weight bonded, nonwoven wafers of synthetic fiber. The sheet is carded to break up the wafers and entangle their residue with the staple fibers. The resulting carded web is then processed to yarn to obtain a slub yarn in which the slubs are the aforesaid residues.

llnited States Patent [1 1 Hartsog 1 Oct. 15, 1974 1 1 SLUB YARN AND METHOD OF FORMTNG A SLUB YARN Inventor: Dawes Coolidge llartsog, l-lockessin,

Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

22 Filed: .lan.29, 1973 21 Appl.l 10.:327,441

[52] U.S. Cl. 57/139, 57/140 BY, 57/144,

57/156, 57/160, 161/170 [51] Int. Cl 002g 3/34 [58] Field of Search............ 57/139, R, 140 ,1,

57/140 BY,143,144,156,157 R,

[56] References Cited UNITED STATES PATENTS 1,997,771 4/1935 McGowan 57/144 2,334,542 11/1943 Cavedon 19/1457 2,923,980 2/1960 Steinbuck 19/99 2,997,837 8/1961 Brecn et a1. r A A 57/144 X 3,199,283 8/1965 Livingston....... 57/140 BY UX 3,251,097 5/1966 Faw et a1 57/140 BY X 3,346,682 10/1967 Thomson 264/93 3,456,434 7/1969 Ncff 57/139 3,627,604 12/1971 Davies 57/157 Primary ExaminerDonald E. Watkins 5 7 ABSTRACT A fibrous sheet of 85-98 percent by weight synthetic fiber staple blended with 2-15 percent by weight bonded, nonwoven wafers of synthetic fiber. The sheet is carded to break up the wafers and entangle their residue with the staple fibers. The resulting carded web is then processed to yarn to obtain a slub yarn in which the slubs are the aforesaid residues.

4 Claims, 3 Drawing Figures PATENIE am 1 51914 FIG.

FIGJ

SLUB YARN AND METHOD OF FORMING A SLUB YARN .FIELD OF THE INVENTION This invention relates to slub yarns made from staple. fibers and to blended fibrous sheets for preparing the slub yarns. More specifically, the invention is directed to a sheet of synthetic staple fibers blended with bonded non-woven wafers of synthetic fiber and to a slub yarn comprising staple fibers entangled with slubs of fibrous masses of residues of bonded fibers.

BACKGROUND OF THE INVENTION Slub yarns are yarns of variable denier which are useful for providing special texture to fabrics. The frequent changes in denier along the length of the yarn provide a raised surface in finished fabric which is quite obvious and pleasing to the viewer. This effect is well recognized, for example, in linen fabrics.

The terms slub and.nep have been used in the prior art to describe an agglomeration of entangled fibers which provide segments along the length of the yarn with increased diameter. Often the term nep has been associated with an undesirable agglomeration along the yarn. On the other hand, the term slub is usually applied to a desirable agglomeration. The art of making slub yarns from natural fibers has been practiced for hundreds of years, and more recently processes have been developed for preparing slub yarns from continuous multifilament synthetic yarns. The present invention, however, is related to staple fiber technology. The staple slub yarns of the prior art have been prepared by variable drafting techniques such as alternately. drafting and releasing separate rovings as they are being spun together, as described in Neff U.S. Pat. No. 3,456,434. Or they have been prepared by dropping slubs cut from soft or unspun sliver into a mass of carded staple as in Cavedon U.S. Pat. No. 2,334,542. Another method was to use a special modification of a carding machine as in Steinruck U.S. Pat. No. 2,923,980 whereby the normal function of the carding machine was altered; instead of promoting formation of parallel fibers along the length of the card web, the improved apparatus promoted formation of entangled agglomerates with fibers in both transverse and longitudinal directions.

In addition, recently techniques have been developed for preparing yarns from nonwoven webs, such as described in Thomson U.S. Pat. No. 3,346,682 and in Davies et al. U.S. Pat. No. 3,627,604, each of which disclose slitting a nonwoven fibrous web to form ribbons and then twisting or other mechanical treatment of the ribbons to form yarns of even denier.

The present invention concerns a sheet of synthetic staple fibers blended with small wafers of a nonwoven synthetic fiber and slub yarns prepared from the blended staple.

SUMMARY OF THE INVENTION The Blended Staple A fibrous sheet comprising about 85-98 percent by weight of synthetic staple fiber blended with about 2-15 percent by weight of bonded, nonwoven wafers of synthetic fiber; said wafers being plate-like in appearance and having a thickness of between about 0.004

and 0.035 inch and an average surface area (measured on oneside) of between about 0.05 and 6 in. said wafers being randomly distributed throughout the sheet.

The 'Process for Preparing Slub Yarn A process for preparing slub yarn comprising:

a. blending synthetic staple fibers with bonded, nonwoven wafers of synthetic fiber to form a sheet having -98 percent weight percent staple fibers and 2-15 percent weight percent wafers,

b. passing the sheet through a carding machine and applying sufficient energy to break the wafers into fibrous masses of bonded fibers entangled with the staple fibers without destroying all fiber bonds, thereby obtaining a carded web, and

c. subjecting the carded web to staple spinning and drafting operations whereby the web is processed into slub yarn.

The Slub Yarn A slub yarn comprising about 85-98 percent by weight of synthetic staple fibers entangled with 2-15 percent by weight of slubs of fibrous masses of bonded synthetic fibers; said slubs being randomly distributed in the yarn in an amount equivalent to at least 1000 slubs per 100,000 yards of yarn; said slubs having a diameter of more than percent larger than that of the base yarn and having a length greater than 1 cm.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a cut-up wafers of bonded nonwoven sheet. These are raw materials used in blends of the invention to prepare slub yarns.

FIG. 2 is a sketch showing a sheet of textile fibers of staple length blended with the wafers.

FIG. 3 is a diagrammatic longitudinal view of a slub yarnprepared from the blended staple of FIG. 2.

DESCRIPTION OF THE INVENTION As shown in FIG. 1, the wafers 1 may be of various shapes. The edges 2 may be cut sharply as shown or may be fuzzy or ragged. The wafers may be prepared by passing a fibrous bonded nonwoven sheet through a rotary cutting-device equipped with a screen to pass along the wafers with a size smaller than the screen holes. They may also be prepared by cutting the nonwoven sheet into continuous ribbons on a slitter and then cutting the ribbons to form wafers. Still another method consists of passing a continous sheet of bonded nonwoven material into a drawbreak machine such as the Pacific Converter which forms multiple ribbons of the sheet about a to 1 inch wide and then breaks these ribbons into strips less than about 4 feet long.

The wafers have the thickness of the original bonded nonwoven sheets, the available sheets being 0.004 to 0.035 inch thick. The shape of the: wafers is not critical. The area of the individual flat surfaces 3 of the wafers may be varied over a wide range, but the average wafer should have a surface area (measured on one side) of about 0.05 to about 6 in..

The cut-up wafers of nonwoven sheet contain numerous filaments 4 which are bonded at crossover points 6 by heat fusion or by an adhesive. The wafers may be derived from heat bonded nonwoven sheets such as the polyester sheets described in Kinney U.S. Pat. No. 3,341,394. These sheets are bonded in hot air as in Krikorian U.S. Pat. No. 3,417,925, FIG. 1. Another satisfactory raw material is the bonded flash spun plexifilamentary sheets of linear polyethylene described in David U.S. Pat. No. 3,532,589. Suitable polypropylene bonded nonwoven sheets are described in Levy U.S. Pat. No. 3,276,944. The wafers may also be made from adhesively bonded sheets which are available in a variety of forms. As is seen, the polymer forming the wafer is not a critical element of this invention. The specific polymers listed above are representative only. Polyesters and polyolefins are, however, preferred, solely because of their availability.

The wafers are blended with textile staple fibers in a conventional air blender. This blend of bonded nonwoven wafers and textile fibers is passed through a picker to form a sheet 11 as shown in FIG. 2. At this point in the process, the wafers 1 have a plate-like quality but they are dispersed throughout the mass of textile staple fibers 5.

The sheet is then passed through a carding machine. The action of the card clothing causes the wafers to break up into fibrous masses comprising residues of bonded fibers entangled with unbonded fibers. It is important that the carding action not destroy substantially all the fiber bonds of the wafer, otherwise the resulting slubs would be too small. These masses are called slubs" and are dispersed randomly throughout the card web, the balance of fibers in the card web being mostly unbonded fibers.

In order to have a sufficient concentration of slubs for attractive textile fabrics, the blend of wafers and textile fibers should have at least 2 percent by weight of wafer. On the other hand, excessive amounts should be avoided so that normal textile processes can be used without excessive stoppage of the machinery. The wafer content in the blend should, therefore, be less than percent.

The staple fibers which are used in theblend are preferably of synthetic organic polymers, since these fibers provide an easily washable shrink-resistant slub fabric. For example the staple fibers may be polyamides such as 6 or 66, polyesters, e.g. polyethylene terephthalate and its copolymers, or polyacrylonitrile and its copolymers.

The card web is handled in normal staple processing equipment (cotton system, woolen, or worsted) to prepare twisted staple yarn, spinning and drafting being essential steps. For example, the card web may be converted in succession card sliver, draw sliver, roving, and twisted staple yarn. The fiber length of the staple must be consistent with the system used. The twisted yarn 7 is shown in FIG. 3. Slubs 8 are spaced randomly along the yarn, being separated by portions of yarn 9 having the base diameter. Staple fiber ends 10 appear throughout the length of the yarn.

Sufficient entanglement occurs between fibers in slubs and the original staple fibers during carding to prevent drop-out of slubs in subsequent processing. The partially disintegrated wafers still retain some of their bonded network character through subsequent textile operations; consequently, after spinning and drafting slubs of varying dimensions are formed in the yarn, and these are randomly situated in the yarn.

The size and frequency of slubs present in the finished yarn are determined by use of the Uster Classimat. The method is described in detail under Test Procedures. The twisted yarns of the invention have at least 1000 slubs per 100,000 yards of yarn with a length greater than 1 cm. and a diameter more than 150 percent larger (preferably more than 250 percent larger) than the base yarn diameter. Products of this type are not produced from pieces of unbonded nonwoven fibrous sheets or from pieces of unbonded knit or woven fabrics.

TESTING PROCEDURES Uster Classimat The frequency of slubs of various sizes is determined by means of the Uster Classimat. The instrument opcrates on the principle that a change in mass passing through the capacitor will cause a change in capacitance. The instrument can sense changes in diameter and length of slubs. The Uster Classimat counts yarn faults (in this case slubs) in as many as 16 classifications of size and length. A given length of yarn is run through the instrument. The instrument reports the number of slubs having diameters in a given range and reports also the length distribution of slubs in each of these diameter ranges. In Table 1 the results are reported for 16 classifications of size and length per 100,000 yards of yarn.

Wafer Surface Area The shredded wafers as obtained from a rotary cutting device are random in shape. The average wafer size can be determined from the starting materials by dividing the total area of uncut wafer material by the number of pieces in the cut-up product. After combin ing with the staple fibers, the determination of average area consists of picking the wafers out of the blended sheet and determining the area of individual wafers, then reporting average values.

Percent by Weight of Wafers The percent by weight of the starting material can, of course, be measured easily by measuring the weight of the uncut wafer material and the weight of the staple fibers. After blending the measurement can only be made by separating the wafers from the staple fibers and weighing the separated components.

EXAMPLES I-IV A nonwoven bonded polyester sheet of the type described in Kinney U.S. Pat. No. 3,341,394 was cut into random shaped wafers and blended with an acrylic staple as indicated in Table l. The bonded polyester material was a random-laid product prepared from about percent by weight continuous filaments of polyethylene terephthalate and 20 percent by weight of continuous filaments of polyethylene terephthalate/polyethylene isophthalate copolymer. The nonwoven polyester sheet used in these examples was bonded before cutting by application of hot air at 220240C. in equipment similar to that described in Krikorian U.S. Pat. No. 3,417,925, FIG. 1. The sheet was exposed in the bonder for a distance of about 2.7 yards measured along the path of the restraining belt. Four different experiments were run as indicated in Table l. The nonwoven sheet for Examples I, II and III weighed 2.2 oz.- /yd. and was 0.012 inch thick. This sheet was bonded by passage through the hot air equipment at about 88 yards/min. The sheet for Example IV weighed 0.8 oz.- /yd. and was bonded by passage through the equipment at about 241 yards/minute.

The bonded nonwoven sheets of Table l were cut up into wafers by passage through a rotary'cutter. The average dimensions of the wafers is indicated in Table I. In Examples I, II and IV the wafers were then blended with a polyacrylonitrile copolymer staple (about 94% acrylonitrile and 6% methylacrylate by weight) having crimped fibers of about 5 cm. length and 2.5 denier per filament. Blending was achieved by passing the wafers and staple fibers through a turbulent air blending device of the type commonly used in textile staple processing and then througha picker. The composition of the picker lap which issued from the picker is indicated in Table 1. This material passed then to a carding machine.

1n Example 111, the nonwoven sheet was cut into large pieces up to one square foot in area, averaging about 0.5 ft. (72 in?) These pieces were then passed through a garnett which shredded them further. The

3.5. The finished yarns contained slubs of varying sizes. The size distribution was determined using the Uster Classimat. Data are reported in Table 1.

Only Examples 1, I1 and 1V produced yarns of this invention, i.e., yarns with more than 1,000 slubs per 100,000 yards of yarn wherein the slubs were at least 1 cm. long and had a diameter at least 150 percent greater than the base yarn diameter. This is shown in the last line of Table 1. The yarn of Example 111 had only 707 such slubs per 100,000 yards of yarn, and it is believed that the low number of slubs in the Example is due to the use of a garnett machine which shredded the wafers too much to be of use herein.

TABLE 1 CHARACTERIZATION OF SLUB YARNS EX. 1 EX. 11 EX. 111 EX. lV

Wafer Description Thickness, inch 0.012 0.012 0.006 Average area, inch 0.07 0.07 0.26 ezJyd. 2.2 2.2 0.8 by weight in blend 5 10 Processing Before Carding Cut, Air Cut, Air Cut, Garnett. Cut, Air Blend, Pick Blend, Pick Air Blend, Pick Blend, Pick Uster Classimat Data Slub Diameter, Slub Length. greater than Base Diam. cm.

100 to 150% 1 10,532 25,091 12,160 41,528 l-2 1,329 2,940 1,307 2,328 2-4 276 657 255 480 4 60 98 27 32 250 to 400% 1 832 2,468 0 1,208 l-Z 978 3,427 27 792 2-4 302 1,103 7 168 4 104 150 O 16 400% and Larger 1 94 366 0 24 1-2 258 1,071 48 2-4 208 826 34 32 4 32 290 27 32 Number of Slubs Over 1 cm. in Lggth With diameter greater than 150% of 4,496 13,572 707 5,088

base diameter With diameter greater than 250% of 1,882 6,867 143 1,080

base diameter shredded material (10 percent by weight) was then blended in anair blower with the same acrylic staple (90 percent by weight) as for Examples 1, I1 and 1V, and the blend was passed through a picker and a carding machine to produce sliver.

Following carding, several ends of card sliver were combined on a draw frame to produce draw sliver for each example. The draw sliver was then further drawn and slightly twisted on a roving frame. Finally the yarn for each example was treated on a spinning frame to produce twisted staple yarn having 12 turns per inch Z twist and a 12/1 cotton count. The twist multiple was Fabrics were woven using undyed denier acetate yarns in the warp and the slub yarns of Table l in the filling. The filling yarns of Table '1 were dyed before weaving. A satin weave was used so that the dyed filling yarns showed primarily on the top surface of the fabric.

Loom construction was filling picks per inch and limitations are to be understood therefrom. The invention is not limited to the exact details shown and described for obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A process for preparing slub yarn comprising:

a. blending synthetic fibers with bonded, nonwoven wafers of synthetic fiber to form a fibrous sheet in the weight percent of 8598 weight percent staple fibers and 2-15 weight percent wafers,

b. passing the sheet through a carding machine and applying sufficient energy to break the wafers into fibrous masses of bonded fibers entangled with the staple fibers without destroying all fiber bonds, thereby obtaining a carded web, and

c. subjecting the carded web to staple spinning and drafting operations whereby the web is processed into slub yarn.

2. The process of claim 1 wherein the staple fibers employed are acrylic fibers and the wafers of synthetic fiber are wafers of polyester fiber.

3. A slub yarn comprising about 98 percent by weight of synthetic staple fibers entangled with 2-15 percent by weight of slubs of fibrous masses of bonded synthetic fibers; said slubs being randomly distributed in the yarn in an amount equivalent to at least 1000 slubs per 100,000 yards of yarn; said slubs having a diameter of more than percent larger than that of the base yarn and having a length greater than 1 cm.

4. The yarn of claim 3 wherein the staple fibers are acrylic fibers and the bonded synthetic fibers are polyester fibers. 

1. A PROCESS FOR PREPARING SLUB YARN COMPRISING: A. BLENDING SYNTHETIC FIBERS WITH BONDED, NONWOVEN WAFERS OF SYNTHETIC FIBER TO FORM A FIBROUS SHEET IN THE WEIGHT PERCENT OF 85-98 WEIGHT PERCENT STAPLE FIBERS AND 2-15 WEIGHT PERCENT WAFERS, B. PASSING THE SHEET THROUGH A CARDING MACHINE AND APPLYING SUFFICIENT ENERGY TO BREAK THE WAFERS INTO FIBROUS MASSES OF BONDED FIBERS ENTANGLED WITH THE STAPLE FIBERS WITHOUT DESTROYING ALL FIBER BONDS, THEREBY OBTAINING A CARDED WEB, AND C. SUBJECTING THE CARDED WEB TO STAPLE SPINNING AND DRAFTING OPERATIONS WHEREBY THE WEB IS PROCESSED INTO SLUB YARN.
 2. The process of claim 1 wherein the staple fibers employed are acrylic fibers and the wafers of synthetic fiber are wafers of polyester fiber.
 3. A slub yarn comprising about 85-98 percent by weight of synthetic staple fibers entangled with 2-15 percent by weight of slubs of fibrous masses of bonded synthetic fibers; said slubs being randomly distributed in the yarn in an amount equivalent to at least 1000 slubs per 100,000 yards of yarn; said slubs having a diameter of more than 150 percent larger than that of the base yarn and having a length greater than 1 cm.
 4. The yarn of claim 3 wherein the staple fibers are acrylic fibers and the bonded synthetic fibers are polyester fibers. 